Method of preventing air from entering an oil suction filter

ABSTRACT

An oil suction filter having an enclosed housing with a base surface and an oil intake opening, a top surface with an oil discharge opening, and a filter usually in the form of a filter cloth in the housing between the intake opening and the outlet. In one form, an oil diverting device at least partially surrounds the oil intake opening. In another form, an oil flow diverting device is provided at either or both of the oil intake opening and the oil outlet. In another form, an oil filter cloth has various densities, thicknesses or layers that control the flow. All the foregoing is for the purpose of minimizing formation of large air bubbles passing through the suction filter. Further, beads in the housing may keep the filter cloth off the base surface.

This application is a divisional of U.S. patent application Ser. No.08/885,785 filed on Jun. 30, 1997, pending.

BACKGROUND OF THE INVENTION

The invention relates to an oil suction filter, in particular forautomatic gearboxes, having a housing which holds a filter and has anoil intake opening on its base surface.

Such filters are generally known. They are used to remove impuritiesfrom oil, sucked out of an oil sump, for example. For this reason, theoil suction filter is arranged with its oil intake opening pointingdownward in the oil sump. The oil is thus sucked out from the undersideof the housing through the filter into a duct which leads on and isarranged for example on the upper side of the housing.

In this process, air bubbles, which accumulate on the underside of thehousing, also pass into the filter and ultimately also to the pump. Theair bubbles themselves arise as a result of mechanical components, forexample gear wheels of an automatic gearbox, which rotate in the oilsump and thus "beat" air into the oil, or as a result of splash oilwhich is used for cooling and is thus fed back into the oil sump.

The air which is also sucked in leads to increased generation of noisein the pump and to increased wear of the pump.

SUMMARY OF THE INVENTION

The object of the invention is to provide an oil suction filter whichreduces the wear of the pump and reduces the production of noise.

This object is achieved by means of an oil suction filter which has anair diverting device that at least partially surrounds the oil intakeopening. This prevents air bubbles which accumulate on the underside ofthe housing and which join together to form large air bubbles frompassing into the filter together with the sucked in oil.

In a preferred exemplary embodiment, the air diverting device completelysurrounds the oil intake opening. In this embodiment, the oil intakeopening is completely shielded, so that no air bubbles which are locatedon the underside of the housing can penetrate into the oil suctionfilter.

In a further preferred exemplary embodiment, the oil intake opening isarranged in an edge region of the underside of the housing. Here, airbubbles are prevented from being sucked in even if the air divertingdevice does not completely surround the oil intake opening. The partwhich lies nearest to the edge of the housing does not necessarily haveto be shielded by the air diverting device. Air bubbles do then alsopass into the filter from the edge region. Since this edge region issmall in comparison to the entire area of the underside, the quantity ofair bubbles is also so small that a significant reduction in noise isachieved.

The air diverting device is preferably designed as a ring whichcompletely surrounds the intake opening. The outer surface of the ringand its central axis extend essentially perpendicularly with respect tothe base surface of the housing. This embodiment can be realized simplyand cost effectively.

In a particularly preferred embodiment of the oil suction filter, thereis provision for beads with an open edge to be provided in the basesurface. This has the advantageous effect that the air bubbles risingfrom the bottom to the top accumulate in the beads and are directed tothe edge of the oil suction filter. Since the beads are open here, theair bubbles are directed past or around the oil suction filter.

In a further preferred exemplary embodiment, the air diverting deviceprotrudes at least approximately 3 mm beyond the base surface, that is,the height of the air diverting device is at least approximately 3 mm.It has in fact been found that the layer of air bubbles forming on theunderside is usually not more than 3 mm. It is therefore essential forthe height to be matched to the thickness of the layer of air bubbles.

Moreover, the object is achieved by an oil suction filter having ahousing with an oil discharge opening, wherein the filter is arrangedbetween the oil intake opening and the oil discharge opening and an oildeflection device is assigned to the oil intake opening and/or the oildischarge opening. This ensures that an inner space of the oil suctionfilter has a uniform flow through it, so that accumulation of air withinthe filter housing is avoided. The air is continuously transported awayin the form of small air bubbles. This prevents a large number of smallair bubbles from joining together to form a large undesired air bubble,in particular in a region with low oil flow which is also referred to asa dead region.

In a preferred embodiment, the oil deflection device comprises a wallregion which runs essentially transversely with respect to the inflow oroutflow direction. This has the effect that oil which is flowing intothe oil suction filter cannot flow directly to the oil discharge openingbut instead is deflected into the inner space, so that a lengthened flowpath of the oil is produced and accumulations of air are avoided.

Finally, the object is to provide an oil suction filter which hasvarious hydraulic resistances, so that a flow can be formed in theentire inner space of the oil suction filter. In addition, the flowvelocity can be influenced selectively by means of the various hydraulicresistances. Consequently, direct discharge of oil from the oil intakeopening to the oil discharge opening, as well as accumulations of air,are avoided.

In a preferred embodiment, the filter is formed from a filter clothwhich has zones of different density and/or thickness in order togenerate the various hydraulic resistances.

When a filter according to the invention is used, it produces a veryuniform flow through the filter so that the formation of large airbubbles is essentially avoided. Moreover, the filtering action of thefilter is extremely effective, that is, essentially all impurities arefiltered out of the oil.

Other features and advantages of the present invention will becomeapparent from the following description of the invention which refers tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained below by means of exemplary embodiments withreference to the drawings, in which:

FIG. 1a is a schematic view of a first exemplary embodiment of an oilsuction filter in an oil sump,

FIG. 1b is a partial view of the oil filter according to FIG. 1a in theregion of a housing opening,

FIG. 2a is a schematic cross section view of a second exemplaryembodiment of an oil suction filter,

FIG. 2b is a perspective view of part of that embodiment,

FIG. 2c is a schematic perspective view of a third exemplary embodiment,

FIG. 3 is a schematic view of a fourth exemplary embodiment of an oilsuction filter and

FIG. 4 is a partial section of the oil suction filter according to FIG.1a along the line IV--IV.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FIG. 1a shows an oil suction filter 1 which is arranged within an oilsump 3 filled with oil.

The oil suction filter 1 comprises a housing 5 which is comprised of twohalf shell shaped parts 7 and 9 which are fitted one on the other andare fixed to one another by means of flanging 11 at their edges.

There is a filter 13 (only shown schematically) within the housing 5which is designed as a cloth and is arranged in an inner space 15 of thehousing 5 which is surrounded by the parts 7 and 9.

The housing 5 has a base surface 17. An opening 19 into the inner space15 is formed in the base surface 17, which lies at the bottom when theoil suction filter 1 is installed in an oil sump 3. The base surface 17therefore forms an underside 17' and faces a base 3a of the oil sump 3.

As shown, the opening 19 is located at an edge region 35 of the basesurface 17 and constitutes an oil intake opening 19'.

A surface 21 of the upper housing part 7 is directed upward and forms anupper side 21'. A further opening 23 in the upper side 21' isdiametrically opposite the opening 19 and leads into a duct 25. Itconstitutes an oil discharge opening 23'.

The openings 23 and 19 are formed here as examples on the upper side 21'or underside 17', respectively. However, it is also possible to make atleast one opening 19 or 23 in a wall region 5' of the housing 5 whichextends obliquely here.

The purely schematically illustrated duct 25 is provided on the surface21 and leads to a pump (not illustrated).

The opening 19 located at the bottom is surrounded by a ring 27, whichforms an air diverting device 27' having a longitudinal axis 29 which islocated essentially perpendicularly to and extending below the basesurface 17. However, it is also possible for the ring 27 to include anannular collar 27a (FIG. 2a) which widens in a funnel shape in thedirection of the base 3a, as this shape collects the air bubblesparticularly effectively.

The ring 27 is securely connected at one of its ends to the base surface17 of the lower housing part 9. It extends downward at least 3 mm in thelongitudinal direction. The ring 27 can be integral with the part 9 ofthe housing 5 or else can be fitted on end, for example, clipped intothe housing 5. An outer surface 31 of the ring 27 thus ensures that theinlet opening 19" which leads into the inner space 15 is located at alower level than the base surface 17 of the lower housing part 9.

Moreover, FIG. 1a shows air bubbles 33. These air bubbles arise as aresult of moving mechanical parts (not illustrated here), for example,parts of an automatic gearbox, which swirl the oil and thus introduceair. These air bubbles 33 rise upward to the surface of the oil owing totheir specific weight. However, the air bubbles 33 which rise fromunderneath the base surface 17 do not pass immediately to the surface ofthe oil but rather accumulate on the underside 17' developing a layer ofair, in which small air bubbles join together to form large ones.

During operation, the pump (not shown) sucks oil out of the oil sump 3through the oil intake opening 19' into the inner space 15 and into theduct 25. During the suction process, the outer surface 31 of the ring 27forms a barrier to the air bubbles 33 which have accumulated on theunderside 17', so that air bubbles 33 cannot pass into the inner space15. In a simple but effective way, this prevents a situation in whichair is also sucked in, which leads to an increase in the production ofnoise.

Of course, the ring 27 can also be in other forms, provided that abarrier is formed which surrounds the opening 19 and which prevents airbubbles 33 from being whirled into the inner space 15. Thus, forexample, the outer surface 31 can become wider or narrower in a funnelshape counter to the inflow direction running upward in FIG. 1a or canrun obliquely upward or downward, rather than perpendicularly withrespect to the base surface 17.

A very good reduction in noise is also achieved if the outer surface 31only partially surrounds the opening 19. A "discontinuous" ring maytherefore be provided. Its outer surface may in particular face a region37 of the underside 17' which has a larger area than a region 37a of theunderside 17'. This design is preferably provided if the opening 19 isarranged in the vicinity of an edge region 35. In this case, the airbubbles which have accumulated in the region 37a would in fact be suckedinto the inner space 15 owing to the absence of a barrier. However,since this region 37a has a relatively small area, the sucked-inquantity of air is also negligibly small.

If a flow is formed underneath the filter, the air diverting device 27'is arranged in such a way that the air bubbles are not flushed into theoil suction filter 1. The air diverting device 27' is therefore providedon the side of the oil intake opening 19' which faces the flow. In thiscase, the oil intake opening 19' does not necessarily have to bearranged in the edge region 35 of the underside 17' of the housing 5. Ifthe air diverting device 27' completely surrounds the oil intake opening19', it does not need to be arranged in the edge region 35 in this caseeither.

FIG. 4 shows, in a further refinement of the oil suction filter, thebase surface 17 which is provided with upraised ribs or beads 68 whichpreferably run parallel to one another. This produces ribs which projectinto the interior of the housing. This refinement holds the filter 13 ata distance from the base surface. This also prevents a filter wall ofthe filter 13 facing the beads 68 from bearing against the inner side ofthe base surface 17. Accordingly, the oil can pass through the filterwall and be sucked away via the duct 25. In order to prevent too muchair from accumulating in the ribs or beads 68 on the underside 17' ofthe base surface, the ribs or beads 68 are designed with edges which areopen toward the edge of the housing. This causes the air whichaccumulates to flow upward past the housing 5.

In FIG. 1b, a region of the opening 19 is illustrated. It is clear thatthe filter 13, which is designed as a filter cloth, and preferably as afilter bag, is attached in a suitable way to a region of the part 9 ofthe housing 5 which bounds the opening 19. This has the effect that oilwhich has been sucked into the oil suction filter flows directly intothe filter bag, flows through the filter walls of the filter bag intothe inner space 15 of the housing (arrows 65, FIG. 1a) and passes to thepump via the duct 25.

Furthermore, in FIG. 1b the ring 27 of the air diverting device 27' isdesigned as a clip on part 66 which comprises at least two latchingprojections 67 which hold the ring 27 on the housing 5 at an edge 100 ofopening 19. This enables the air diverting device 27' to be attachedeasily.

FIG. 2a shows a further embodiment of an oil suction filter 1'. Itcorresponds essentially to the example explained in conjunction withFIG. 1a, so that parts referred to by the same reference symbols are notdescribed again.

The difference in this embodiment is that an oil deflection device 41ais inserted into the oil intake opening 19' of the oil suction filter 1and an oil deflection device 41b is inserted into the oil dischargeopening 23'. The oil deflection devices 41a and 41b are formed by atubular section 39a or 39b and a wall region 45a or 45b which runsessentially transversely to the inflow or outflow directions of the oiland also forms a ceiling which is connected to the section 39a. As aresult, the oil is directed through an oil inlet opening 47, downstream,viewed in the direction of flow, of the oil intake opening 19', into theinner space 15 and deflected by approximately 90° with respect to theperpendicular inflow direction. The oil deflection device 41b, which isassociated with the oil discharge opening 23', forms at its wall regionan oil outlet opening 49 which is offset with respect to the oildischarge opening 23', so that overall a lengthened oil flow path in theinner space 15 is produced. The oil deflection device 41a or 41b alsohas the function of deflecting the inflowing oil in such a way that theentire inner space of the oil suction filter 1 has a uniform flowthrough it. In particular, the intention is that the flow through thefilter 13 will be uniform and at a relatively low velocity.

The oil deflection device 41a, which is basically identical in design tothe oil deflection device 41b, is shown only partially in FIG. 2b. Thewall region 45a is of half shell shaped design, and longitudinallyrunning ribs 43 are provided on the shell. This shape prevents theinflowing oil from flowing away directly upward to the opening 23 butinstead deflects it mainly to the side.

The advantage of the oil deflection device 41a is that the uniform flowthrough the inner space prevents an accumulation of air and thus theformation of relatively large air bubbles. The air is insteadcontinuously transported away in the form of small air bubbles. As aresult, a large number of small air bubbles cannot join together to forma large air bubble which, if it were to pass through the oil suctionfilter 1, would have adverse effects in terms of the noise behavior andcause wear of the pump.

FIG. 2c shows a modified exemplary embodiment of an oil deflectiondevice 41a with a wall region 45' which spans the opening 19 and forms aceiling. The wall region 45' is realized by means of a hood 51 whichcomprises a base plate 53 and an edge 55 surrounding the plate. The hood51 is preferably connected by its edge 55 to the tubular section 39a ofthe oil deflection device 41a. The peripheral edge 55 runs preferably ata right angle with respect to the base plate 53. It is of integralconstruction with the base plate 53. Through openings 57, whichpreferably have different opening cross sectional areas, are provided inthe base plate 53 and in the edge 55. As a result, various hydraulicresistances are formed, which distribute the inflowing oil virtually inthe entire inner space 15 (FIG. 2a). Preferably, the through openings 57which are nearer to the tubular section 39a have a smaller openingcross-sectional area than those which are further away. In particular,the opening cross-sectional area of the through openings 57 becomeslarger with increasing distance from the section 39a. As a result,approximately the same quantity of oil is let into the filter from eachthrough opening 57.

The oil deflection device 41a according to FIG. 2c is preferablyassociated with the oil intake opening 19'. A preferably identicaldesign oil deflection device 41b is associated with the oil dischargeopening 23'. Of course, oil deflection devices 41a, 41b in accordancewith FIG. 2b may be combined with oil deflection devices like those wereexplained with reference to FIG. 2c.

FIG. 3 shows a further exemplary embodiment of an oil deflection device41' which is realized using a filter 13'. The filter 13' is insertedinto the inner space 15 of the oil suction filter 1. The oil deflectiondevice 41' is formed by the filter 13' including regions with differenthydraulic resistances. The hydraulic resistances can be formed using afilter cloth 59 which has zones with different densities and/orthicknesses. The different densities are realized, for example, bypressing the filter cloth 59 together at least in certain regions.Alternatively, a filter cloth may also be used which comprises variousmaterials of different densities/thicknesses.

Alternatively, the filter 13' can be formed using a filter cloth 59which comprises at least one region 61 with a different number of filtermats 63. The individual filter mats 63 can preferably be bonded to oneanother, riveted or connected in some other way.

The regions having a higher flow resistance of the filter 13' arerealized by means of regions with thicker, denser and/or more filtermats. At these regions, less oil can be sucked through the filtermaterial. This also permits a long flow path to be realized in the innerspace 15 of the oil suction filter 1, and it is possible to alsoinfluence the flow velocity of the oil. Consequently, relatively largeair bubbles can be avoided by means of a continuous and uniform flow ofoil in the inner space 15 of the oil suction filter 1.

Of course, it is also possible to provide an oil suction filter whichcomprises the air diverting device 27', the oil deflection device 41a,41b and/or the filter 13'. There may also be provision for the oilsuction filter to comprise at least two of these devices.

These devices can therefore be combined freely with one another.

Although the present invention has been described in relation toparticular embodiments thereof, many other variations and modificationsand other uses will become apparent to those skilled in the art. It ispreferred, therefore, that the present invention be limited not by thespecific disclosure herein, but only by the appended claims.

What is claimed is:
 1. A method of preventing air from entering an oil suction filter, the oil suction filter comprising a housing having an edge around the housing, the housing having a base surface, the housing defining an enclosed interior, the base surface having an inner side facing into the interior of the housing and having an outer side opposite the inner side, an oil intake opening into the interior through the base surface, an oil outlet from the housing, and a filter disposed in the housing between the oil intake opening and the oil outlet for filtering oil passing therethrough, the method comprising the steps of:directing air at the outer side of the base surface away from the oil intake opening and upward past the housing using at least one concave bead formed in the base surface, which projects into the interior of the housing, and which extends along the base surface to the edge of the housing in a direction away from the oil intake opening, the bead being open at the outer side of the base surface and at the edge of the housing, and diverting air at the base surface from the oil intake opening using an air diverting device at least partially surrounding the oil intake opening. 